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The effect of a leptin single nucleotide polymorphism on quality grade, yield grade, and carcass weight of beef cattle

P. J. Kononoff^*,1, H. M. Deobald, E. L. Stewart, A. D. Laycock and F. L. S. Marquess

^* Department of Animal and Nutritional Sciences, University of New Hampshire Ritzman Laboratory, Durham 03824; and and Quantum Genetics Research Inc., Saskatoon, SK, Canada S7N 4N1

¹ Correspondence and current address: Dept. of Anim. Sci., P.O. Box 830908, Univ. of Nebraska, Lincoln 68583 (phone: 402-472-6442; fax: 402-472-6362; pkononoff2{at}unl.edu).

Feedlot producers could optimize the value of cattle in a given market grid if they were able to improve the uniformity of the body composition between cattle among loads. Allelic variation due to a single nucleotide transition (cytosine [C] to thymine [T] transition that results in a Arg25Cys) has been demonstrated to be associated with higher leptin mRNA levels in adipose tissue and increased fat deposition in mature beef, but the effect on economically important carcass traits has not been investigated in either market-ready steers or heifers. Therefore, the objective of this study was to determine the effects of a leptin SNP on the quality grade (QG), yield grade (YG), and weight of beef carcasses. A slaughter trial was conducted using 1,435 crossbred finished heifers and 142 crossbred finished steers as they entered the slaughter facility. Canada QG tended (main effect of genotype P = 0.16, but P < 0.01 for both CC vs. TT and CT vs. TT) to be affected by leptin genotype. Specifically, 7.6 and 7.1% more TT carcasses graded Canada AAA or higher than the CT and CC carcasses, respectively, which supports the suggestion that the leptin SNP is associated with carcass fat. The proportion of carcasses grading Canada YG 1, 2, or 3 was affected (P < 0.01, P = 0.05, and P = 0.02 for YG 1, 2, and 3) by leptin genotype. The proportion of TT carcasses of Canada YG 1 was 12.5 and 15.1% lower than that of CT and CC carcasses, respectively, indicating that rearing animals under the same management and feeding system may result in greater carcass fat and a lower probability of the proportion of carcasses grading YG 1 within certain genotypes. The carcass weights of animals with the CC genotype tended (P = 0.07) to be higher than those of the TT genotype (365.5 vs. 362.3 kg). No significant difference was observed between the TT and CT genotypes in carcass weight. The observed associations between leptin genotype and carcass characteristics may represent an opportunity to genetically identify animals that are most likely to reach specific marketing groups.

Key Words: Beef • Carcass • Leptin • Marbling • Quality Grade • Yield Grade

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				J. L. Lusk Association of single nucleotide polymorphisms in the leptin gene with body weight and backfat growth curve parameters for beef cattle J Anim Sci, August 1, 2007; 85(8): 1865 - 1872. [Abstract] [Full Text] [PDF]